7 Discussion

Age-specific mortality data for the elderly in the United
States is generally considered to be of poor quality [8]. The primary sources
for this data are the decennial census and death registration. The census data have been
inconsistent, though Shrestha and Preston [25] identify
underreporting in 1970 as the primary source of problems. In this paper we examined sets
of cohort and period age-specific mortality rates calculated from the Medicare Enrollment
Data Base, an extremely large administrative base. We compare the mortality curves across
regions within race and sex groups, and we compare national mortality curves of white men
and women relative to black and Puerto Rican men and women. The Medicare EDB is a
promising source of age-specific mortality data at oldest ages, but questions remain about
the age-specific mortality patterns of blacks, especially black men.

We compared
mortality curves across regions and among cohorts for evidence of consistency. There has
been a debate focused on the black crossover in age-specific mortality at older ages, a
pattern found in these data. There are two primary arguments. The first holds that this
pattern is real and reflects the selection of less frail blacks relative to white
Americans by age 80 or so [10]. The second
argument is that the crossover is an artifact of age misreporting [2]. Any crossover
pattern between regions within the same race and sex would also suggest age misreporting.

Both the period and cohort age at death data for whites in the Medicare EDB appear to
be very consistent, at least up to age 95, perhaps higher for women. Above age 100 the
patterns become extremely inconsistent.

Both cohort and period mortality curves of white women and men showed great consistency
across regions. Some regions had lower mortality rates, but there was little year-to-year
variation and no mortality crossover. Where inconsistencies occurred, they were primarily
from the western regions of the U.S. that had small populations when social security
numbers, which is the regional identifier, were issued to this population.

The African-American mortality crossover is found in every period and cohort comparison
of the national population. This crossover pattern is remarkably consistent, occurring at
ages 85 or 86 in every cohort and period comparison. Recall that Kestenbaum [10] examined this
issues using the EDB for specific years, concluding that the pattern was real and that the
age data were accurate. However, mortality rates by the mid-90s for black men drops below
the mortality rates of white women, a pattern that is unlikely.

The regional patterns for both black men and women show considerable variation over
time. This is especially so for men. While we limited this regional comparison to regions
with significant black populations, the variations could have been a function of size.
Indeed, at the national level, the period mortality patterns of black women are smoothed
considerably. The patterns for men remain inconsistent.

This data set is not sufficient to determine whether the black mortality crossover is
real or due to age misreporting. And the considerable inconsistency across regions also
creates concern about these data. When aggregated at the national level, the mortality
curves for black women may be okay up to age 90. In general, we conclude that further
examination of the black data is necessary before using them for substantive analysis.

The mortality curves of Puerto Rican men and women are not smooth. That is, they are
not consistent from year to year, but rise and fall. However, these year-to-year
variations are not large and may simply reflect the relative size of the population. The
comparison of the pattern of white American with Puerto Ricans does not reveal a
cross-over, but indicates that Puerto Rican mortality rates for both men and women are
basically the same or lower than the rates for whites. Again, reasons for these patterns
are not clear, but this is a pattern reported in previous research. The annual variations
and the relatively low mortality patterns lead us to conclude that these data should be
used with caution until further examinations can be conducted.

Considering the magnitude of size of the Medicare EDB, that it captures the majority of
the elderly population of the U.S., and that it contains birth and death information, it
is clearly a valuable resource for evaluating the age patterns of mortality among older
Americans, particularly for older white Americans. It is unlike any other database
currently available for research of this kind and its value cannot be overemphasized.
However, we recognize the limitations of the database, in particular the concerns it has
raised over the black age-at-death data. Certainly, more research can be done to
investigate these concerns to determine the nature of the mortality patterns that emerge
for black Americans. Given its limitations, the Medicare EDB should be only one of many
tools included in further investigations.